RF Mixer Self-Test Using Delayed LO Signals and DC Readout
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for testing radio frequency (RF) devices, such as mixers, are costly and time-consuming, requiring expensive test fixtures and equipment, which can be a bottleneck in manufacturing high-frequency RF integrated circuits.
Innovation Solution
A built-in self-test (BIST) circuit with a buffer and delay elements is integrated into RF devices, allowing for self-testing by coupling delayed signals to mixers, changing phase shifts to detect failures, and using DC values to assess mixer functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional test fixtures and equipment are used for testing RF devices, then measurement precision can be achieved, but device complexity and testing cost increase significantly
Solution Approach 1:
The RF device performs self-testing using built-in test circuits that generate test signals and measure device performance without requiring external test equipment. The mixer under test generates its own test signals through local oscillator inputs, and the test results are read through DC voltage measurements at the mixer output, enabling the device to test itself autonomously
Solution Approach 2:
A simple DC voltage measurement serves as an intermediary to indicate the performance status of the mixer. Instead of directly measuring complex RF parameters requiring expensive equipment, the patent uses DC voltage levels at the mixer output as a proxy indicator of mixer functionality and gain, simplifying the measurement process significantly
2Reliability
If conventional test equipment is used for RF device testing, then reliable test results are obtained, but productivity decreases due to time-consuming testing
Solution Approach 1:
The patent replaces complex mechanical RF test setups with electronic self-testing circuits integrated on the same chip. The test function is implemented through electronic signal generation and measurement within the RF device itself, eliminating the need for external mechanical test fixtures, probes, and calibration equipment that slow down the testing process
Solution Approach 2:
The test circuits and signal paths are pre-configured within the RF device during manufacturing, allowing immediate self-testing without requiring setup, calibration, or preparation of external test equipment. The mixer and local oscillators are designed to generate test signals as part of their normal operation, enabling instant testing readiness
3Productivity
If built-in self-test circuit is integrated into RF devices, then productivity improves by reducing testing time, but device complexity increases due to additional circuitry
Solution Approach 1:
The local oscillator circuits serve dual purposes: generating signals for normal RF mixing operation and generating test signals for self-testing. The same mixer that performs frequency conversion also performs the mixing function for test signal generation when provided with appropriate local oscillator inputs, eliminating the need for separate dedicated test signal generators
Solution Approach 2:
The self-test function uses simplified versions of the normal signal paths already present in the RF device. The test signals follow the same mixing path as operational signals, and the DC voltage measurement copies the essence of RF performance testing without requiring full RF measurement capability, reducing circuit complexity while maintaining test effectiveness
4Measurement precision
If external test equipment is used for RF device testing, then measurement precision is maintained, but loss of time occurs due to equipment calibration and maintenance
Solution Approach 1:
The RF device autonomously performs its own testing without requiring external equipment that needs calibration and maintenance. The built-in test circuits generate test signals and measure performance continuously, eliminating downtime associated with scheduling and performing tests with external equipment that requires periodic calibration and maintenance
Solution Approach 2:
The self-test function can be performed continuously or at any desired interval without interrupting normal device operation or requiring equipment setup. The test circuits remain active and ready, allowing immediate testing whenever needed, whereas external test equipment requires setup, calibration verification, and maintenance intervals that interrupt productive action
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient self-testing of RF devices with minimal additional circuitry, saving power and chip area, and reducing the need for external testing equipment, thereby improving production throughput and reducing testing time.
Implementation Method 1
a buffer configured to buffer a reference signal from a local oscillator (LO) to produce a first RF signal at a first frequency
Implementation Method 2
a plurality of delay elements having different respective transmission delays, the delay elements each having a first end coupled to the output terminal of the buffer and a second end configured to provide a respective delayed signal based on the first RF signal
Implementation Method 3
each of the plurality of mixers having a first input terminal, a second input terminal, and an output terminal... mixing, using the plurality of mixers, the plurality of respective delayed signals with a second RF signal having the first frequency
Implementation Method 4
the self-test circuit is configured to, in the test mode, change a phase shift of the buffer from a first value to a second value, in order to detect failure of the mixers
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A radio frequency (RF) device includes a plurality of mixers, each of the plurality of mixers having a first input terminal, a second input terminal, and an output terminal; and a self-test circuit. The self-test circuit includes a buffer having an input terminal and an output terminal, the buffer configured to buffer a reference signal from a local oscillator (LO) to produce a first RF signal at a first frequency; and a plurality of delay elements having different respective transmission delays, the delay elements each having a first end coupled to the output terminal of the buffer and a second end configured to provide a respective delayed signal based on the first RF signal, where the self-test circuit is configured to, in a test mode, couple the second ends of the delay elements to respective first input terminals of the plurality of mixers to provide each mixer with the respective delayed signal, and where the second input terminals of the mixer are configured to receive a second RF signal having the first frequency.